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mbraak's solution

to Custom Set in the OCaml Track

Published at Nov 24 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

Create a custom set type.

Sometimes it is necessary to define a custom data structure of some type, like a set. In this exercise you will define your own set. How it works internally doesn't matter, as long as it behaves like a set of unique elements.

Getting Started

For installation and learning resources, refer to the exercism help page.

Installation

To work on the exercises, you will need `Opam` and `Base`. Consult opam website for instructions on how to install `opam` for your OS. Once `opam` is installed open a terminal window and run the following command to install base:

``````opam install base
``````

To run the tests you will need `OUnit`. Install it using `opam`:

``````opam install ounit
``````

Running Tests

A Makefile is provided with a default target to compile your solution and run the tests. At the command line, type:

``````make
``````

Interactive Shell

`utop` is a command line program which allows you to run Ocaml code interactively. The easiest way to install it is via opam:

``````opam install utop
``````

Consult utop for more detail.

Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

test.ml

``````open OUnit2

module type EXPECTED = sig
type t
val of_list : int list -> t
val is_empty : t -> bool
val is_member : t -> int -> bool
val is_subset : t -> t -> bool
val is_disjoint: t -> t -> bool
val equal : t -> t -> bool
val add : t -> int -> t
val intersect : t -> t -> t
val difference : t -> t -> t
val union : t -> t -> t
end

module CSet : EXPECTED = Custom_set.Make(struct
type t = int
let compare a b = compare (a mod 10) (b mod 10)
end)

let assert_true exp _text_ctxt = assert_equal exp true
let assert_false exp _text_ctxt = assert_equal exp false
let tests = [
"sets with no elements are empty">::
assert_true (CSet.is_empty (CSet.of_list []));
"sets with elements are not empty">::
assert_false (CSet.is_empty (CSet.of_list [1]));
"nothing is contained in the empty set">::
assert_false (CSet.is_member (CSet.of_list []) 1);
"when the element is in the set">::
assert_true (CSet.is_member (CSet.of_list [1;2;3]) 1);
"when the element is not in the set">::
assert_false (CSet.is_member (CSet.of_list [1;3;3]) 4);
"empty set is a subset of an other empty set">::
assert_true (CSet.is_subset (CSet.of_list []) (CSet.of_list []));
"empty set is a subset of a non empty set">::
assert_true (CSet.is_subset (CSet.of_list []) (CSet.of_list [1]));
"non-empty set is a not subset of an empty set">::
assert_false (CSet.is_subset (CSet.of_list [1]) (CSet.of_list []));
"set is a subset of set with exact same elements">::
assert_true (CSet.is_subset (CSet.of_list [1;2;3]) (CSet.of_list [1;2;3]));
"set is a subset of larger set with exact same elements">::
assert_true (CSet.is_subset (CSet.of_list [1;2;3]) (CSet.of_list [4;1;2;3]));
"set is not a subset of set that does not contain its elements">::
assert_false (CSet.is_subset (CSet.of_list [1;2;3]) (CSet.of_list [4;1;3]));
"the empty set is disjoint with itself">::
assert_true (CSet.is_disjoint (CSet.of_list []) (CSet.of_list []));
"the empty set is disjoint with non-empty set">::
assert_true (CSet.is_disjoint (CSet.of_list []) (CSet.of_list [1]));
"non-empty set is disjoint with empty set">::
assert_true (CSet.is_disjoint (CSet.of_list [1]) (CSet.of_list []));
"sets are not disjoint if they share an element">::
assert_false (CSet.is_disjoint (CSet.of_list [1;2]) (CSet.of_list [2;3]));
"sets are disjoint if they do not share an element">::
assert_true (CSet.is_disjoint (CSet.of_list [1;2]) (CSet.of_list [3;4]));
"empty sets are equal">::
assert_true (CSet.equal (CSet.of_list []) (CSet.of_list []));
"empty set is not equal to non-empty set">::
assert_false (CSet.equal (CSet.of_list []) (CSet.of_list [1;2;3]));
"non-empty set is not equal to empty set">::
assert_false (CSet.equal (CSet.of_list [1;2;3]) (CSet.of_list []));
"sets with the same elements are equal">::
assert_true (CSet.equal (CSet.of_list [1;2]) (CSet.of_list [2;1]));
"sets with different elements are not equal">::
assert_false (CSet.equal (CSet.of_list [1;2;3]) (CSet.of_list [1;2;4]));
assert_true (CSet.equal (CSet.of_list [3]) (CSet.add (CSet.of_list []) 3));
assert_true (CSet.equal (CSet.of_list [1;2;3;4]) (CSet.add (CSet.of_list [1;2;4]) 3));
"adding existing element does not change set">::
assert_true (CSet.equal (CSet.of_list [1;2;3]) (CSet.add (CSet.of_list [1;2;3]) 3));
"intersection of two empty sets is empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.intersect (CSet.of_list []) (CSet.of_list [])));
"intersection of empty set with non-empty set is an empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.intersect (CSet.of_list []) (CSet.of_list [3;2;5])));
"intersection of non-empty set with empty set is an empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.intersect (CSet.of_list [1;2;3;4]) (CSet.of_list [])));
"intersection of sets with no shared elements is empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.intersect (CSet.of_list [1;2;3]) (CSet.of_list [4;5;6])));
"intersection of set with shared elements is set of shared elements">::
assert_true (CSet.equal (CSet.of_list [2;3]) (CSet.intersect (CSet.of_list [1;2;3;4]) (CSet.of_list [3;2;5])));
"difference of two empty sets is an empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.difference (CSet.of_list []) (CSet.of_list [])));
"difference of empty set and non-empty set is empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.difference (CSet.of_list []) (CSet.of_list [3;2;5])));
"difference of non-empty set and empty set is the non-empty set">::
assert_true (CSet.equal (CSet.of_list [1;2;3;4]) (CSet.difference (CSet.of_list [1;2;3;4]) (CSet.of_list [])));
"difference of two non-empty sets is the sets of elements only in the first set">::
assert_true (CSet.equal (CSet.of_list [1;3]) (CSet.difference (CSet.of_list [3;2;1]) (CSet.of_list [2;4])));
"union of two empty sets is an empty set">::
assert_true (CSet.equal (CSet.of_list []) (CSet.union (CSet.of_list []) (CSet.of_list [])));
"union of empty set and non-empty set is non-empty set">::
assert_true (CSet.equal (CSet.of_list [2]) (CSet.union (CSet.of_list []) (CSet.of_list [2])));
"union of non-empty set and empty set is the non-empty set">::
assert_true (CSet.equal (CSet.of_list [1;3]) (CSet.union (CSet.of_list [1;3]) (CSet.of_list [])));
"union of two non-empty sets contains all unique elements">::
assert_true (CSet.equal (CSet.of_list [1;2;3]) (CSet.union (CSet.of_list [1;3]) (CSet.of_list [2;3])));
]

let () =
run_test_tt_main ("custom_set tests" >::: tests)``````
``````open Base

module type OrderedType =
sig
type t

val compare : t -> t -> int
end

module type S =
sig
type elt
type t

val of_list : elt list -> t
val is_empty : t -> bool
val is_member : t -> elt -> bool
val is_subset : t -> t -> bool
val is_disjoint: t -> t -> bool
val equal : t -> t -> bool
val add : t -> elt -> t
val intersect : t -> t -> t
val difference : t -> t -> t
val union : t -> t -> t
end

module Make(Ord: OrderedType) =
struct
type elt = Ord.t
type t = {
l: elt list;
}

let elt_equals v1 v2 =
(Ord.compare v1 v2) = 0

let empty_set = { l=[] }

let is_member s v =
List.exists s.l ~f: (fun v' -> elt_equals v v')

if is_member s v then
s
else
{ l = List.cons v s.l }

List.fold_left l ~init: s1 ~f: add

let of_list l =

let is_empty s = List.is_empty s.l

let is_subset s1 s2 =
List.for_all s1.l ~f: (fun v -> is_member s2 v)

let is_disjoint s1 s2 =
List.for_all s1.l ~f: (fun v -> not (is_member s2 v))

let equal s1 s2 =
List.length s1.l = List.length s2.l && is_subset s1 s2

let intersect s1 s2 =
List.fold_left s1.l ~init: empty_set ~f: (fun r v ->
if is_member s2 v then
else
r
)

let difference s1 s2 =
List.fold_left s1.l ~init: empty_set ~f: (fun r v ->
if is_member s2 v then
r
else
)

let union s1 s2 =
end``````